Secretory Activity of Mesenchymal Stromal Cells with Different Degree of Commitment under Conditions of Simulated Microgravity.

Microgravity negatively affects the bone tissue which manifested in a decrease in mineral density of the bones during long-term space flights. Impairments of bone homeostasis are determined among other things by changes in secretory activity of heterogeneous populations of low-committed precursors, such as mesenchymal stromal cells (MSC) and osteoblasts. We studied the effect of microgravity modeling during 10 days on paracrine activity of osteogenically committed and intact MSC. Cell response to simulated microgravity depended on the degree of commitment. The response of osteogenically committed MSC was less pronounced and manifested in increased production of sclerostin. In intact MSC, an increase in IL-8 and VEGF secretion and a decrease in osteoprotegerin level were detected. These changes can underlie the shift of bone homeostasis towards bone resorption.

Extracellular Matrix Proteins and Transcription of Matrix-Associated Genes in Mesenchymal Stromal Cells during Modeling of the Effects of Microgravity.

We studied the effects of simulated microgravity (10 days) on the production of extracellular matrix proteins and expression of extracellular matrix-associated genes in human mesenchymal stem cells. A decrease in collagen production, reduced expression of TIMP-1, TIMP-3, and MMP-11 genes, and enhanced expression of tenascin and laminin subunit were revealed. The results attest to activation of proteolytic processes in the matrix of mesenchymal stromal cells and weakening of cell adhesion to extracellular matrix under conditions of simulated microgravity.